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bt-sdp: fix broken uuids power-of-2 calculation

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The binary search in sdp_uuid_match() only works when the number of
elements to search is a power of two.

  lo = record->uuid;
  hi = record->uuids;
  while (hi >>= 1)
      if (lo[hi] <= val)
          lo += hi;

  return *lo == val;

I noticed that the record->uuids calculation in
sdp_service_record_build() was suspect:

  record->uuids = 1 << ffs(record->uuids - 1);

Unlike most ffs(val) - 1 users, the expression is ffs(val - 1)!

Actually ffs() is the wrong function to use for power-of-2.  Use
pow2ceil() to achieve the correct effect.  Now the record->uuid[] array
is sized correctly and the binary search in sdp_uuid_match() should
work.

I'm not sure how to run/test this code.

Cc: Andrzej Zaborowski <balrog@zabor.org>
Cc: qemu-stable@nongnu.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1427124571-28598-2-git-send-email-stefanha@redhat.com
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2015-03-23 15:29:23 +00:00 committed by Kevin Wolf
parent ecdda9e03d
commit 588ef9d411
1 changed files with 1 additions and 1 deletions
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2
hw/bt/sdp.c
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@ -707,7 +707,7 @@ static void sdp_service_record_build(struct sdp_service_record_s *record,
len += sdp_attr_max_size(&def->attributes[record->attributes ++].data,
&record->uuids);
}
record->uuids = 1 << ffs(record->uuids - 1);
record->uuids = pow2ceil(record->uuids);
record->attribute_list =
g_malloc0(record->attributes * sizeof(*record->attribute_list));
record->uuid =